Coloured scanning electron micrograph (SEM) of Serratia marcescens, Gram-negative, facultative anaerobic prokaryote (bacterium). Serratia species occur as commensal fauna in the intestinal mucosal lining of man and mammals. It also occurs in soil, water, on plants and has a characteristic red pigment. S. marcescens is occasionally pathogenic in humans, as a nosocomial infection and septicaemia. It can be associated with urinary and respiratory tract infections, endocarditis, osteomyelitis, septicaemia, wound infections, eye infections, conjunctivitis, keratitis, endophthalmitis, and tear duct infections, and meningitis. In the 1950s S. marcescens was erroneously believed to be non-pathogenic and its reddish coloration was used in school experiments to track infections for demonstrating the importance of hand washing. In corals, it is the cause of the disease known as White pox. Magnification: x5, 000 when shortest axis printed at 25 |